Field of the Invention
The present invention relates to driving device, and in particular to a power supply device with control based on setting resistor.
Description of Related Art
Light emitting diodes (LEDs) have high luminous efficiency, long service time, widely operation temperature and environmental mercury-free, making them beyond the incandescent and fluorescent light bulbs, and led lighting field into a new solid-state lighting era.
General lighting fixtures, such as incandescent lamps, fluorescent bulbs or lamps are usually driven by alternative current (AC) electric power, however, the LEDs are driven be direct current (DC) electric power. Thus, an essential condition for replacing incandescent lamps, fluorescent bulbs or lamps with LED lighting fixture is that the LED lighting fixture can directly connected to AC electric power.
LEDs are semiconductor devices with low turn on voltage, and can emit light when an electrical current is passed through it in a specific direction. Moreover, LEDs are also current dependent devices with their light output intensity being directly proportional to the forward current flowing therethrough. Since the LEDs cannot have totally same parameters (such as internal resistance) even in the same manufacturing process, the same type of lighting fixtures with the LEDs cannot provide light with the same luminous intensity.